Administrative Core Unit A fulfills three important roles for the Center. First, the Administrative Core is responsible for the ascertainment and retention of participants for all components of the study. During the first day of testing. Administrative Core staff collect saliva samples from the twins, their biological siblings, and their biological parents, and mail the samples to Dr. Shelley Smith's laboratory at the University of Nebraska Medical Center so that DNA samples can be extracted, processed, and analyzed by Project IV staff. The second major responsibility of Administrative Core A is to ensure that all study data are efficiently collected, verified, and consolidated across the six research projects, and to coordinate the synthesis and distribution of an updated summary data file with data from all Research Projects every three months. Finally, in collaboration with staff on Service Core B, Service Core A staff coordinate cross-project data sharing and implement and monitor the Center-wide protocol for data sharing with external collaborators and other qualified investigators in the field.